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Posted: 9/10/2006 4:51:57 PM EDT
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Hello- I have searched and searched but cannot find this info...what is the fragmentation range of the 6.8 SPC cartridge? Will it fragment at 300 yards? 400? Thanks in advance. |
I don't know the range that it will fragment. Right now I have the Hornady TAP LE binder in front of me and it looks like the 6.8 round isn't a big fragmenter at least not like some 5.56. Heres a test of 110gr 6.8SPC Tap in a 16" DPMS the test is bare gelatin velocity: 2,537 penetration: 14.5" retained weight: 66.8 % frag: 39% Maxium performance range: 350yds sorry I couldn't give you what you wanted but I have a good bit of data about the TAP 6.8 round, if you need anything else just ask |
Why would you worry about it? The 6.8 TAP has better terminal ballistics than the 75gr TAP at all ranges (and the 75gr TAP has better terminal performance than MK262). |
does the "maximum performance range" equal the range at which the bullet fragments significantly? |
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james_b0nd, Cartridges do not have fragmentation ranges--the bullets loaded into cartridges are what demonstrate different upset windows, depending on their intended use. Many of the bullets used in the 6.8 mm continue to deform and/or fragment down to 2100 f/s or less. Having been among the first researchers to study the terminal effects of heavy 5.56 mm projectiles, as well as being the first to assess the 6.8 mm, there is NO doubt that well designed 6.8 mm ammunition offers superior terminal performance in every respect to any equivalent 5.56 mm load. |
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Thanks for weighing in, DocGKR. Always appreciated. Can you shed any light on why the military has seemingly shelved a more widespread adoption of 6.8mm, aside from a recent Army (?) study that once again found that 5.56mm ammunition is sufficient for current cobmat needs? From what we read here on Arfcom, the M855 is just about the worst terminal ballistics round one could choose, but the military keeps giving it the thumbs up. |
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BushMeister, Please tell us more about this, "recent Army (?) study that once again found that 5.56mm ammunition is sufficient for current combat needs". 5.56 mm NATO 62 gr SS109/M855 “Green Tip” FMJ was designed over 20 years ago as linked machine gun ammunition to be fired from the FN Minimi/M249 SAW while engaging enemy troops wearing body armor during conventional infantry combat at distances of several hundred meters; it was not originally intended for use in carbines or rifles. In its intended role, it works reasonably well. Notwithstanding some recently released distorted, incomplete, inaccurate, and contradictory misinformation being spoon fed to the gullible masses, have you or anyone else personally seen any actual DOD test data that truly demonstrates the 5.56 mm M855 to be the best choice for combat use in carbines? |
If you want a rough and dirty idea of its effectiveness as far as tissue damage Id suspect the best performing 6.8 loads offer about 150% the tissue damage as the best 5.56 loads 75 grain TAP and MK262)and the .308 155 TAP offers about 200% more damage of the best 5.56 loads (75 grain TAP and MK262). For a given barrel length expect the 6.8 to perform at a range of 50-100 yards further than 5.56 and .308 to perform further still in suitable length barrels (16"+). Someone please correct me if I am too far off base with that humongous generalisation.  |
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Are the shorter barrels (12") getting the same good results out to 100+ yards? Sorry if its been covered in one of the other threads....but you guys have put out ALOT of info and its easy to get lost in it. Assuming a person could find the ammo, the right optics and shoot appropriatly, said person could have a 12" SBR filling the roles of short entry weapon, home defense weapon, and medium range carbine.... I say as I eyeball an empty lower. |
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Excerpted from Hornady's description of "Maximum Performance Distance": "This is based on bullet retained velocity at distance and the associated expansion, penetration and fragmentation performance at that velocity. The distance given indicates the point out to which the terminal performance will closely match that as shown in these test results. Beyond this distance the terminal performance will slowly decrease, as velocity decreases, causing less expansion, fragmentation and greater penetration. This was determined by evaluating the results of lower velocity shorter barreled weapons coupled with exterior ballistic calculations..." Using Hornady's own data for max performance range, BC, velocity, etc. it appears the 6.8 110gr load fragments reliably to 1900fps and most likely even lower. Using Hornady's "max performance range" formula for the 11.5" barrel coupled with Hornady TAP 5.56mm 75gr #8126N, we get a "max performance range" of 150 yards. If someone has a consensus average maximum FPS for 12" 6.8SPC barrels we could work out its "max performance range" the same way quite easily. I suspect it will be quite a bit further than 5.56mm 11.5" barreled firearms. |
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I'm a bit surprised by the tome of your response. I am not regurgitating rumors or falsehoods. I am not a terminal ballistics expert, but I agree that the adoption of the M855 (and the use of 14.5" barrels with this round) has cost the lives of some of our soldiers and Marines. Here is information about the recent Army test (Article is from June 8, 2006): "The Army has completed a detailed study of the effectiveness of its standard-issue M855 5.56mm ammunition cartridge that is used in the M16 and the M4 rifles. The study found no significant difference between the M855 and commercially available 5.56mm rounds during close fighting." Picatinny Army Study Also: Strategy Page Here is the text of the Picatinny article. Perhaps you can gain more inside information on the test. Obviously, it happened, and determined exactly what I posted. We may disagree with the conclusions, but there it is. Army study affirms effectiveness of M855 5.56mm ammo  The Army has completed a detailed study of the effectiveness of its standard-issue M855 5.56mm ammunition cartridge that is used in the M16 and the M4 rifles. The study found no significant difference between the M855 and commercially available 5.56mm rounds during close fighting. A team of military, scientific, medical, engineering and law enforcement experts conducted the study for the Army's Project Manager, Maneuver Ammunition Systems located here. "All of the rounds studied performed in a band of effectiveness that will produce excellent results in real-life situations", Col. Mark D. Rider said. The study sought to answer whether any commercial, off-the-shelf 5.56mm bullets that perform better than M855 against unarmored targets in Close Quarters Battle might be available. It was limited further to determining if the Army could quickly purchase and field a possible replacement for the M855 and did not consider replacing the current inventory of 5.56mm weapons with weapons of another caliber. "This was not a caliber study" Rider said. "However, it did find that the current family of 5.56mm weapons and the older 7.62mm M14 have the same potential effectiveness in the hands of a Warfighter during the heat of battle." The study also showed an increase in lethal potential when the marksmanship technique of firing controlled pairs, i.e. firing two rounds in rapid succession, was used. Rider said the Army will continue to study variations in performance that some Soldiers and Marines to criticize the M855 while the overall majority are satisfied with its effectiveness. He also noted that researchers believe that interaction between the weapon and the bullet may be the root cause of "through-and-through." In arriving at these conclusions, the team developed ground-breaking tools and methodologies that apply sophisticated modeling and equipment normally reserved for the study of high-dollar systems such as tanks and artillery to less costly weapons for the very first time. As a result, new standards for testing small caliber ammunition are emerging that will help bring the science of more costly system to individual weapon. Rider said that his organization is beginning to study how commercially available rounds perform against common battlefield barriers like body armor, car doors, and windshield glass compared to the M855. Answers to these questions will help improve the lethal capability of the ground forces for decades into the future, he said. ***END EXCERPT*** Again, my question to you regards the reasons why the 6.8mm seems to have been sidetracked. Are there issues besides the results of this test (beyond the usual fear of change and meeting of logistics and operational challenges) in more widely adopting the new caliber? |
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6.8 mm has demonstrated significantly better terminal performance compared to 5.56 mm in all testing I am aware of to date; any reasons to "sidetrack" it are not based on objective science. The 6.8 mm meets a validated requirement as requested in a Mission Needs Statement by a SOF combat commander. As I noted above, COL Rider's comments above may not be fully accurate or reflect the full test data...perhaps he should have read www.amazon.com/Lipstick-Pig-Winning-No-Spin-Someone/dp/0743271165/sr=1-1/qid=1158352037/ref=pd_bbs_1/103-6222874-5381463?ie=UTF8&s=books. I highly recommend folks interested in 6.8 mm read the superb article by Zak Smith: demigod.org/~zak/archive/sgn_68spc.pdf |
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Thanks for the response and that Zak Smith article. My layman's understanding of all I've read is that the 6.8mm should be fast-tracked ASAP, especially if the Army/Marines want to go on using 16" and shorter barrels. Unfortunately, the Army (at least) has recently decided that the M855 is not only good enough for current combat engagements, but equally capable compared to commercially available, heavier 5.56mm rounds. As Col. Mark D. Rider said, "this is not a caliber study", so it didn't directly address the issue of 5.56mm M855 versus 6.8mm. But the fact that the study decided that the 75 & 77 grain 5.56mm rounds we have all been talking about offer no advantage over M855 (thought here on Arfcom to be just about the worst terminal ballistics 5.56mm round) indicates that the Army has different testing and evaluation criteria than proponents of the 6.8mm. Aside from the issue of terminal ballistics, there may be issues related to the weight of the 110-grain 6.8mm rounds versus 62-grain 5.56mm rounds in the mimimal 210 round capacity carried by our ground troops (and some apparently carry twice as many rounds). I wonder what the weight of each of these rounds in volume would be. I get a weight of 7.4 lbs. for 7 loaded 30-rd 5.56mm mags. In addition, there may be issues with designing a reliable 30-round magazine for the 6.8mm. I believe that there are relaible 25-round magazines at present, but perhaps the military would be reluctant to issue magazines with a different capacity than those that have been issued for decades. |
This does not appear to be an accurate statement.
Again, this is not a correct interpretation. Gel test methadology has been standardized with all test facilities using the same criteria. In addition, the problem of M855 is not poor terminal performance, but excessively variable terminal effects.
This is not an issue: 30 rds of 5.56 mm M855 = 0.79 lbs, 26 rds of 115 gr 6.8 mm = 0.98 lbs, 20 rds of 7.62 mm M80 ball = 1.05 lbs.
6.8 mm mags are available that reliably work with 25, 26, 28, and 30 rounds. As noted above, the currently used M14, Mk11, M110 SASS, Mk17 SCAR-H, and HK417 mags all have a 20 round capacity...thus this is a moot point. Think beyond the box... |
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All this leads me to yearn for the 6.8mm (.270) SPC family of rounds and their characteristics and FAQs to be added to the ammo-oracle.com. Is anyone working on this? Ammo-oracle authors seem to be careful to qualify the data and strive for apples to apples comparisons. For instance, the 7.62 x 51 M14 round was judged no better than the 5.56 M855 for steel penetration, EXCEPT for when the 7.62 AP round was substitued for the 7.62 FMJ ball round. Would there be any political resistance from arfcom, et.al. to do this, since there are fortunes currently tied up in the continuance of the 5.56 round? |
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CCW, In terms of what people here have money tied up in, and to the extent that the people here train, 5.56 is a complementary system to 6.8, for a person who decides 6.8 is the way to go. 5.56 will remain cheaper to shoot than 6.8 SPC for the forseeable future. Thus it makes sense to shoot 5.56 to make bulk training more affordable, while not neglecting essential checks with 6.8. I think it's pretty obvious that the Oracle authors are objective, in any case. -z |
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